Touch screen with selective touch sources

ABSTRACT

The present invention provides a touch sensor system that distinguishes from among distinct users. As a vehicle touch sensor system, the present invention provides a touch sensor accessible from a driver position and a passenger position, a first contact point driven with a first signal and associated with the driver position, a second contact point driven with a second signal and associated with the passenger position, and a processor configured to discern users in the driver position touching the touch sensor from users in the passenger position touching the touch sensor based on detection of the first or second signals on the touch sensor. For example, the vehicle touch sensor system can be a navigation system. Distinguishing the driver from the passenger can allow touch inputs from the driver to be disabled when the vehicle is in motion, for example.

This application is a continuation of U.S. patent application Ser. No.10/052,695, filed Jan. 18, 2002 now abandoned, which claims the benefitof U.S. Provisional Application 60/304,007 filed Jul. 9, 2001, each ofwhich are hereby incorporated in their entirety.

FIELD OF INVENTION

This invention relates to a touch screen or touch digitizer withselective touch sources. The invention more particularly relates to atouch system that utilizes information from a touch sensor and a contactpoint in order to determine the position of a touch to the touch sensor.

BACKGROUND OF INVENTION

Touch screens are capable of measuring touch position for a singletouched point. Current touch screens are unable to effectively determinethe position of touches by multiple users, discriminate among touches bymultiple users, or enable the touch of one user while disabling thetouch of another, especially when simultaneous touch down occurs. Anumber of touch screen applications would benefit from the ability todetermine the position of multiple touches to a touch screen,discriminate among touches by multiple users and to enable touches byone user and not another.

Infrared and surface acoustic wave touch screen systems have the abilityto locate two separate simultaneous touches in two of four possiblelocations, but they are unable to resolve the locations uniquely due to“shadow” effect. A capacitive touch system with the ability todiscriminate between human touch and the simultaneous use of aninanimate object (a stylus) is disclosed in U.S. Pat. No. 5,365,461 byStein et al. The system is an improvement of the definite capacitivedisclosures in U.S. Pat. Nos. 4,371,746, 4,293,734, 4,198,539, and4,071,691 to Pepper, Jr. These capacitive systems lack the ability tomeasure coordinates of two simultaneous human touches because thecurrent flowing through the touch screen from each touch are combined,and the measured result indicates an average of two touch locations. Atouch system addressing disadvantages of known touch systems and theircomponents would be an important advance in the art.

SUMMARY OF THE INVENTION

The present invention relates to systems and methods of distinguishingdifferent users of a touch screen system. In a particular embodiment,the present invention provides a vehicle touch screen system thatincludes a touch sensor accessible from a driver position and apassenger position, a first contact point driven with a first signal andassociated with the driver position, a second contact point driven witha second signal and associated with the passenger position, and aprocessor configured to discern users in the driver position touchingthe touch sensor from users in the passenger position touching the touchsensor based on detection of the first or second signals on the touchsensor. In one example, the contact points can be embedded in the driverand passenger seats.

Vehicles systems of the present invention can be used to disable touchinputs from the driver while the vehicle is in motion, still allowingthe passenger to interact with the system. For example, in a method ofthe present invention involves providing a touch sensor accessible froma driver position and a passenger position, distinguishing touch inputsby users in the driver position from touch inputs by users in thepassenger position, disabling touch inputs from users in the driverposition when the vehicle is in motion, and allowing touch inputs fromusers in the passenger position regardless of whether the vehicle is inmotion. Distinguishing touch inputs by users in the driver position fromtouch inputs by users in the passenger position can involve driving afirst user contact point associated with the driver position with afirst signal, driving a second user contact point associated with thepassenger position with a second signal, and detecting the presence ofthe first or second signal transferred by a touch input.

The above summary of the present invention is not intended to describeeach disclosed embodiment or every implementation of the presentinvention. The Figures and the detailed description that follow moreparticularly exemplify these embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be more completely understood in consideration of thefollowing detailed description of various embodiments of the inventionin connection with the accompanying drawings, wherein like numeralsrepresent like parts throughout several views, in which:

FIG. 1 is a schematic diagram including the primary features of a touchsystem, according to the invention;

FIG. 2 is a schematic diagram including the features of an alternativeembodiment of a touch system, according to the invention;

FIG. 3 is a schematic drawing of a touch system of the prior art;

FIG. 4 is a schematic circuit representation of a touch system of theprior art;

FIG. 5 is a schematic drawing of a touch system, according to theinvention;

FIG. 6 is a schematic circuit representation of the touch system ofFIGS. 1 and 5, according to the invention;

FIG. 7 is a detailed representation of the touch system embodiment ofFIG. 2, according to the invention;

FIG. 8 is a schematic circuit representation of the touch system ofFIGS. 2 and 7, according to the invention;

FIG. 9 is a perspective view of a touch system according to theinvention where the touch sensor and contact point are mounted on thesame substrate.

While the invention is amenable to various modifications in alternativeforms, the specifics thereof have been shown by way of example in thedrawings and will be described in detail. It should be understood,however, that the intention is not to limit the invention of theparticular embodiments described. On the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is generally applicable to touch screens or touchdigitizers with selective touch sources. The invention is particularlyrelated to a touch system having a touch sensor and a user contactpoint, where the system utilizes information from both the user contactpoint and a touch to the touch sensor to determine a location of a touchto the touch sensor. The invention may be particularly suited for usewith a capacitive touch system where both the touch sensor and the usercontact point are touched, which may additionally create enhancedperformance of the touch system. The present invention may also beparticularly suited for use in, for example, an electronic game systemdesigned to be played by one or more players where, in the course ofplaying the game, players can apply touch input to generate a responsein the game.

In a touch system, the location of a touch applied by a user isgenerally determined by measuring separate signals generated by a touchinput to the system, and comparing the signals, or ratios of thesignals, to calculate the position of the touch. The touch data then maybe, for example, correlated to a particular action or instruction.Assuming a properly calibrated touch system, the calculated position ofa touch should be sufficiently close to the actual touch location to beused for a particular action or instruction as a reported touchlocation. What qualifies as “sufficiently close” is determined in partby the resolution of the touch system. As used herein, reporting a touchlocation refers to the calculated touch location being used by the touchsystem in an appropriate manner, for example, by the applicationsoftware, to determine the user input instructions. Reporting mightinclude communications from a touch system processor to a centralprocessing unit (CPU), or in a more integrated system can simply entailtouch position data being calculated and appropriately used ascontemplated by the application.

A “touch” to the touch sensor or to the contact point may include anactual physical touch, or may be defined as a proximity touch, wherein atouch signal is generated in the touch sensor or the contact point whena user or object is positioned sufficiently close to generate a signal.

As used herein, “information” related to a contact point and a touchsensor that is used to determine a position of a touch to the touchsensor may include several distinguishing characteristics and includesany suitable measurable or detectable parameter, quantity or property.For example, “information” may include the magnitude, frequency, orphase of a touch signal from a “touch” to the touch sensor or to thecontact point. The “information” may also relate to the timing of touchdown and lift off from a touch sensor or contact point or whether or nota “touch” is in an active or inactive area of a touch screen or contactsurface for a given function of the touch system. Fundamentally, the“information” may include whether or not any “touch” has been made to aparticular touch sensor or contact point.

Now referring to the schematic diagram of FIG. 1, one example of a touchsystem 10 of the present invention includes a touch sensor 12, a contactpoint 14, a processor 16 and a power source 18. The lines connectingthese elements represent communication between the elements, for examplethrough wires. Touch sensor 12 may be an infrared touch sensor, a forcetouch sensor (i.e., one that determines a touch position by measuringflex, strain, and/or displacement due to the force of a touch), aresistive touch sensor, a surface acoustic wave (SAW) touch sensor, acapacitive touch sensor or the like. The touch sensor may be transparentto allow interaction with an image, or it may be non-transparent as inthe case of touch pads and digitizers. A capacitive touch system mayinclude a touch sensor 12 that has a conductive surface, typically madeby applying transparent Indium Tin Oxide (ITO) or Tin Antimony Oxide(TAO) onto a glass substrate. The conductive surface is then typicallyovercoated with a dielectric material. Touch sensor 12 may, in thealternative, be configured as a multiple electrode near field imaging(NFI) capacitive system or an X-Y array, such as is used in athrough-glass discrete button, as an alternative to the current sensingcapacitive system described with reference to FIGS. 3-9 below.

Contact point 14 may be configured to be activated by a touch, typicallyfrom a user. Contact point 14 may be a touch sensor, proximity sensor,or other device or object that may receive input or other means forgenerating a touch signal in the touch system. Contact point 14 may takethe form of an object whose function is apparent to the user, or maytake a form that is less visible to the user and/or less apparent as toits functionality in the touch sensor system. Contact point 14 istypically electrically connected to the touch system and may bepositioned in the touch system at a separate location from the touchsensor 12. When contact point 14 and touch sensor 12 are physicallyseparated, it may be easy to distinguish between touch signals generatedby each contact point and the touch sensor. Physical separation of thesecomponents may also be advantageous for certain applications of thepresent invention, such as a multi-user game.

An example of positioning contact point 14 and touch sensor 12 atseparate locations from each other includes placing the contact point inone housing and placing the touch sensor in a separate housing. In thisarrangement, the contact point and touch sensor may still beelectrically connected to each other and to the touch system with, forexample, a wire or cord. In a second example, contact point 14 and touchsensor 12 are each positioned within the same housing, but arephysically separated from each other in a way that they do not share thesame substrate. In this second example, the contact point and touchsensor may also be electrically connected to each other and to the touchsystem.

Contact point 14, in an alternative embodiment, may be positioned on thesame surface, screen, conductive surface, or the like as touch sensor12. According to this alternative embodiment, contact point 14 would beat a location on touch sensor 12 that is permanently or temporarilyinactive for the purposes of generating a response in the system due toa touch input at that location, but would create a touch signal that isunique to the contact point. As a result, a touch signal from contactpoint 14 can be distinguished from a touch signal from touch sensor 12even though they are both positioned on the same surface or screen.Thus, information from the area of the contact point may be used todetermine a position of a touch to an active area of the touch sensorand/or to determine a system instruction due to the reported touch. Forexample, touching the contact point area may provide “enhancement” ofthe touch signal generated by touching the touch sensor so that athreshold signal is attained for the system (for example, necessary fora given function of the system), or that a signal-to-noise ratio of thesystem is increased so that the system may more accurately determine theposition of a touch to the touch sensor. One means of distinguishingbetween touches to touch sensor 12 and contact point 14 in thisalternative embodiment would be to require that either the touch downevents or the lift off events from the touch sensor and contact pointare timed separately. As a result, the system may be able to determinewhich touch signal was generated first, determine the general positionof each of those touches (for example, within or outside an “active”area set aside for the touch sensor), and subtracting the touch signalfrom either the touch sensor or the contact point from the total touchsignal generated in the system in order to accomplish an objective ofthe touch system.

Touch system 10 may also include a processor 16 that is electricallyconnected to touch sensor 12 and contact point 14. Processor 16 maygather information from touch sensor 12 and contact point 14. Processor16 may be able to distinguish the identity of the signals, the magnitudeof the signals, the timing of the signals being created, as well asother information related to touch sensor 12 and contact point 14.Processor 16 may then process the information as gathered and generatean output, for example, instructions or a particular action for thetouch system.

Touch system 10 may also include a power source 18 that provides powerto the system. Power source 18 may typically be a voltage source, theoutput from which being at a level that correlates with the requirementsof the touch system.

In another embodiment of the invention, touch system 100 includes atouch sensor 112, a first contact point 114, a second contact point 115,a processor 116 and a power source 118, as shown in the schematicdiagram of FIG. 2. Touch sensor 112 is configured to receive a touchthat generates a touch signal. Touch sensor 112 may be one of a varietyof touch sensors, such as a touch sensor for force, infrared, resistive,surface acoustic wave, or capacitive touch system technology. Contactpoints 114 and 115 may be activated by a touch that generates a touchsignal in the touch system. Contact points 114 and 115 are typicallyelectrically connected to touch system 100 and the system may be able todistinguish between touches to the contact points. Touch system 100 mayalso include processor 116 that gathers information from the touchsensor 112 and contact points 114 and 115. Typically, the position of atouch to touch sensor 112 cannot be determined until at least one orboth of contact points 114 and 115 are also activated. Processor 116 isable to identify, measure the magnitude of, and determine the sequentialorder of information from touch sensor 112 and contact points 114 and115. The system may also be able to distinguish between a touch by auser A to contact point 114 and a touch by a user B to contact point 115by uniquely driving each user through their respective contact point.Touch system 100 may be powered by a power source 118 that “drives”touch sensor 112 and/or contact points 114 and 115 with power, such aswith a voltage source.

A capacitive touch system 200 is illustrated in the schematic drawing ofFIG. 3. Touch system 200 includes touch sensor 212, processor 216, powersource 218, conductive surface 213 on touch sensor 212, electrodes 220,amplifiers 222, and wires 224 that connect the amplifiers to the touchsensor 212. Touch system 200 also includes current measuring devices 228that measure currents 226 from touch sensor 212, voltage 227,capacitance 230 between the user and the touch sensor 212, ground 232,body impendence 234 from a user, body-to-ground impedance 236, earthground 238, system impedance 240, and central processing unit (CPU) 242.An approximate circuit representation including some components of touchsystem 200 is included as FIG. 4.

Typically, electrodes 220 are bonded to and electrically connected withconductive surface 213. Electrodes 220 serve two purposes: first, theyconnect the conductive surface to amplifiers 222 through wires 224; andsecond, the electrodes are arranged around the edge of conductivesurface 213 in a pattern that distributes the current flowing in theconductive surface in a linear, orthogonal flow. The construction ofcapacitive sensors in electrode patterns is known to those skilled inthe art, as disclosed in U.S. Pat. Nos. 4,198,539 and 4,371,746, both toPepper, Jr.

System 200 also includes power source 218 that produces a time varyingsignal v(t). This signal may be a sine wave, square wave, or any timevarying voltage. Amplifiers 222 drive the signal to each of the cornersof conductive surface 213 through wires 224. The voltage v(t) is drivenfrom the output of each of amplifiers 222, so the entire surface oftouch sensor 212 is at a uniform voltage. Current measuring devices 228measure currents 226 that flow through the amplifier outputs. Whenconductive surface 213 is touched by, for example, a finger, capacitivecontact is made and is represented by capacitor 230. Current flows fromground 232, through amplifiers 222, conductive surface 213, touchcapacitor 230, through body impedance 234 and body to ground impedance236, and from earth ground 238 through system impedance 240. Currentsmeasured by devices 228 are converted into digital format and processor216 calculates a position of a touch to touch sensor 212 using ratios ofthe current 226 generated from a touch to touch sensor 212. Processor216 may send position information to a CPU 242 for further processing.

If the touch system 200 is connected directly to a grounded wall outlet,impedance 240 may be close to zero. If the touch system 200 is within asmall device, such as a battery-powered device with an insulatingplastic case, impedance 240 may be very high, which will limit thecurrent flow. Limited current flow in this situation also limitsperformance and sensitivity of touch system 200.

One embodiment of a capacitive touch system is the touch system 300shown in the schematic drawing of FIG. 5 and generally described withregard to FIG. 1. Capacitive touch system 300 includes touch sensor 312,contact point 314, processor 316, power source 318, conductive surface313 of touch sensor 312, and electrodes 320 electrically coupled totouch sensor 312. Touch system 300 also includes amplifiers 322, wires324 connecting amplifiers 322 to touch sensor 312, system currents 326,voltage 327 from power source 318, current measuring devices 328, touchcapacitance 330, local ground 332, body impedance 334, body-to-groundimpedance 336, earth ground 338, system impedance 340 and CPU 342. Touchsystem 300 further includes several features different from the priorart, including touch sensor switch 344, contact point switch 346,amplifier 348 for contact point 314, current detector 350, signaladjuster 352, contact point voltage 354, contact point current 356, andcontact point capacitance 358. Switches 344 and 346 and touch sensor 314make it possible for touch system 300 to function in several modes,whereas touch system 200 can function in only one mode. In a first mode,touch system 300 functions in the same way as prior art capacitive touchsystem 200. However, in alternative user-selectable modes, touch system300 is able to overcome many of the shortcomings found in prior arttouch systems. Touch system 300 also includes amplifier 348 that drivestouch pad 314, and output current 356 from contact point 314 is measuredby current measuring device 350.

As discussed above, a “touch” to touch sensor 312 or contact point 314,as referred throughout this application, may include an actual physicaltouch, such as by a user's finger or another object held by the user, ormay be defined as a “proximity” touch that creates a touch signal withinthe circuit without actually physically touching the touch sensor orcontact point. Contact point 314 may be designed as a button, a mouse, ajoystick, a glove, a switch or other device that may be “activated” byuser contact or proximity in order to create a “touch” signal that maybe processed by processor 316.

Table 1 indicates some possible operating modes of the touch system 300of FIG. 5. Modes of operation 1-3 depend on the state of switches 342and 344 and on the relationships of voltages 327 and 354, thesensitivity of current detectors 328 and 350, and on the algorithmsperformed by processor 316 and by CPU 342. In an alternative embodiment,the modes of operation may depend on the frequency or the phase ofvoltage 327 and 354 and the frequency or phase sensitivity of currentdetectors 328 and 350. A touch system utilizing phases will be describedthroughout the remainder of the specification.

TABLE 1 Touch System with Touch Sensor and One Contact Point Circuitconfiguration (refer to FIG. 5) Sensor Sensitivity and ResponsivenessSwitch 344 Switch 346 (refer to FIG. 5) What is Phase of 328 Phase of350 Touch Sensor Contact Point Mode Powered Phase of 327 Phase of 354312 314 1 Touch Sensor Closed Open Any Touch Must also 312 90° 270°touch Contact  0° DC Point 312 2 Contact Point Open Closed Must also AnyTouch 314 270°   90° touch Contact DC  0° Point 314 3 Touch SensorClosed Closed Any touch; Any touch; 312 and 90° 270° (More (More ContactPoint  0° 180° sensitive if sensitive if 314 Contact Point Touch Sensor314 is also 312 is also touched) touched)

In a first mode of touch system 300 (mode 1), any touch to touch sensor312 is detected and located, and a touch to contact point 314 isdetected only if touch sensor 312 is also being touched or a touchsignal from sensor 312 has been generated. Switch 344 has been closed sothat time varying voltage 327 from power source 318 is connected toamplifiers 322, which may be unity gain amplifiers. Touch sensor 312 isdriven with the time varying voltage 327 such that a touch to conductivesurface 313 will cause current 326 to flow through touch sensor 312,touch capacitance 330 to the body of the user touching surface 313, bodyimpedance 334, body-to-ground impedance 336, earth ground 338, systemimpedance 340, local ground 332, and back to amplifiers 322. Touchsensor current 326 and contact point current 356 are measured by currentmeasuring devices 328 and 350, respectively.

Processor 316 collects information from current measuring devices 328and 350 and calculates a touch position of a touch to touch sensor 312based on the ratio of currents 326. Current measurements 326 and 356 areused to detect touches to contact point 314 and touch sensor 312.Current measurements 326 and 356 may also be used by a processor 316 todetermine the sequence of touches to touch sensor 312 and contact point314, the duration of those touches, the magnitude of those touches, andother information that might be useful for activating or providinginstructions to touch system 300 for a user utilizing touch system 300.The system may also be configured to continuously measure the positionof signals from touch sensor 312 and contact point 314 in order todetermine the time of touch down or lift off. In this configuration, itis possible for contact point 314 to be included on the same sensor astouch sensor 312, so long as the signal generated by the contact point314 is different or distinguishable from the signal of touch sensor 312.

Touch system 300 may also include a phase or frequency shifter 352 thatadjusts the relationship of voltage 354 relative to voltage 327, whilemaintaining a constant waveform of voltage 327. Typically, the phase ofvoltage 354 is set to be distinguishable from voltage 327 by a certainamount in order to maximize the net voltage between touch sensor 312 andcontact point 314, for example, by 180°. Table 1 includes examples ofvarious phase shifts in a typical phase setting according to theinvention. Signal adjuster 352 may also change the magnitude of voltage354 relative to voltage 327. Amplifiers 322 and 348 typically havenegligible phase shifts or frequency shifts. Current measuring devices328 and 350 may make current measurements in a variety of ways,including incorporating a synchronous demodulator in order to detect thephases of currents 326 and 356.

The detection phases of devices 328 and 350 may be individuallyadjustable. In mode 1, the detection phase of devices 328 are typicallyset to detect capacitively coupled current from the source (touch sensor312) to ground (ground 332). Touch current is largely capacitivelycoupled, and is typically shifted from voltage 327 by 60° to 80°. Thephase difference can be as little as 30° in cases where impedance 336and 340 are largely resistive. For purposes of example in thisdisclosure, multiples of 90° phase shifts will be used. In a preferredembodiment of mode 1, the detection phase of device 350 is set to[voltage 327+270°]. Device 350 detects capacitively coupled currentflowing from touch sensor 312 to contact point 314. In alternativeembodiments implementing a frequency sensitive circuit, various standardincrements in the magnitude of the voltage frequency may be used todistinguish the signals generated by touch sensor 312 and contactsurface 314.

In a second mode of touch system 300 (mode 2), a touch to contact point314 is detected, and a touch to touch sensor 312 is then detected.Switch 346 is closed in this mode so that voltage 354 is conveyedthrough amplifier 348 to contact point 314. Switch 344 is open so thatamplifiers 322 are not powered by voltage 327, thus allowing touchsensor 312 to have a zero time-varying signal. As a result, a touch totouch sensor 312 while not touching contact point 314 results in nomeasurable signal and no touch is detected by system 300. Signaladjuster 352 may modify the voltage phase or voltage frequency ofvoltage 354 so that the phase or voltage is distinct from the phase orvoltage of voltage 327. Preferably, in a phase sensitive circuit, thephase of current measuring devices 322 is set at 90°.

When contact point 314 is touched, current 356 flows from local ground332, through amplifier 348, contact point 314, touch capacitance 358,and through the user's body impedance 334. Current 356 may follow twoseparate paths after passing through body impedance 334. If the usertouches only contact point 314, then current 356 flows through theuser's body-to-ground impedance 336, to earth ground 338, systemimpedance 340, and back to local ground 332. Current 356 resulting fromthe touch to contact point 314 is measured by current measuring device350. This measurement is conveyed to processor 316 that is configured todetect a touch to contact point 314 based on the change of current 356.Processor 316 may convey this change in current to CPU 342, and CPU 342may use this information to trigger changes in a program, change theimage on a display, or give other instructions that might be requiredfor proper use and function of touch system 300. For example, a touch tocontact point 314 may indicate that one user of touch system 300, forexample in a video game scenario, is ready to play the video game. Inresponse, CPU 342 may change an indicator on the display from red togreen to indicate that the user is now able to participate.

If the user touches contact point 314 and touch sensor 312simultaneously, or if there are overlapping touches, a portion ofcurrent 356 also flows from the user's body, through touch capacitance330 to touch sensor 312. Current 356 is distributed to amplifiers 322based on the touch location to touch sensor 312, and then flows back tolocal ground 332. As current 356 passes through amplifiers 322, it willbe measured by current measuring devices 328, and the measurements willsubsequently be conveyed to processor 316. Thus, a touch to touch sensor312 can be detected and then the position of that touch measured, onlyif the user is simultaneously touching contact point 314 and touchsensor 312. It is noted, however, that a path for return of the currentprovided by touching contact point 314 and touch sensor 312 may increasethe current being channeled through touch sensor 312. As such, thehigher amount of current may increase the amount of signal being sent toprocessor 314 while the amount of “noise” in the system remainsconstant. As a result, the signal-to-noise ratio of the currentmeasurements and the resulting position measurements may be increased.

In a third mode of the touch system (mode 3), touch sensor 312 andcontact point 314 are both driven with voltage signals, preferably byclosing switches 344 and 346. A touch to touch sensor 312 alone may bedetected and measured, as will a touch to only contact point 314. Signaladjuster 352 may adjust the phase or frequency of voltage 354 to bedistinguishable from voltage 327. In the case of a phase sensitive touchsystem, voltage 354 is preferably out of phase with voltage 327 by 180°.

A benefit of mode 3 is improved signal-to-noise ratio for touch signalson touch sensor 312, if a user simultaneously touches or is in proximitywith contact point 314. Signal-to-noise ratios are affected in at leasttwo ways. First, touching a contact point 314 while touching touchsensor 312 provides a local ground path for touch current, asillustrated in the schematic circuit drawing of FIG. 6. Second, inaddition to touch current flowing from touch capacitance 330, through auser's body impedance 334 into earth ground 338, and through systemimpedance 340 to local ground 332, current may also flow from sensorcapacitance 330, through a user's body impedance 334, through contactpoint capacitance 358, amplifier 348 and into local ground 332.Accordingly, a higher signal is provided to touch sensor 312, and thesensitivity of touch sensor 312 is enhanced. Sensitivity of touch sensor312 is enhanced in part when earth ground 338 is bypassed when a user istouching both contact point 314 and touch sensor 312, when voltage 354is passed through contact point 314 and the user to touch sensor 312, ora combination of these effects on system 300. This is especially truewhere system impedance 340 is high, as in the case with ungroundedbattery operated equipment, causing a high percentage of current 340 topass through touch sensor 312 rather than back to system ground 332.

An alternative embodiment of the touch system of the present inventionillustrated in FIG. 2 is described in further detail according to themore detailed schematic drawing of touch system 400 illustrated in FIG.7. Touch system 400 is a capacitive touch system that operates with manyof the same features and functions as the touch system of FIG. 5. Likefeatures are described with the same reference numbers. In addition tothe features of FIG. 5, touch system 400 further includes an additionalcontact point 415, amplifier 460, current measuring device 462, contactpoint touch capacitance 464, signal modifier 466, contact points switch468, contact point current 470 and contact point voltage 472. Anapproximate circuit representation including some components of thetouch system of FIG. 7 is illustrated in FIG. 8.

Touch system 400 may operate in any of several user-selectable modesthat overcome the technology limitations found in prior art systems.Some of the details related to a capacitive touch system of touch system400 are presented in Table 2.

TABLE 2 Operating Modes for Touch System with Touch Sensor and TwoContact Points Circuit configuration (refer to FIG. 7) Switch SwitchSwitch 444 446 468 Sensor Sensitivity and Phase of Phase of Phase ofResponsiveness 428 450 462 (refer to FIG. 7) What is Phase of Phase ofPhase of Sensor Mode Powered 427 454 464 11a Pad 52 Pad 53 1 TouchClosed Open Open Any touch Must Must Sensor 412 90°  270° 270° touchtouch 0° DC DC Touch Touch Sensor Sensor 412 412 2 Contact Open ClosedOpen Must Any touch Must Point 414 90°  270°  90° touch touch 0° 180° DCContact Contact Point 414 Point 414 3 Contact Open Open Closed Must MustAny touch Point 415 90°   90° 270° touch touch 0° DC 180° ContactContact Point 415 Point 415 4 Contact Open Closed Closed Must Any touchAny touch Points 414 270° & 270° 180° touch and 415 180°  180°  90°Contact 0° Point 414 or 415 5 Touch Closed Closed Closed Any touch Anytouch Any touch Sensor 412 90°  270° 270° and Contact 0° 180° 180°Points 414 and 415

In a first mode of touch system 400 (mode 1), touch system 400 operatesin the same way as prior art capacitive touch screens, such as touchsystem 200. According to this mode, switch 444 is closed and switches446 and 468 are left open. As a result, touch sensor 412 is activated bya touch and processor 416 is able to determine the location of a touchto touch sensor 412 (see mode 1 of touch system 300 for furtherdetails).

In a second mode of touch system 400 (mode 2), similar to mode 2 oftouch system 300, switch 446 is closed and switches 444 and 468 areopen. A touch to contact point 415 or touch sensor 412 can be detectedand measured only if the user is simultaneously touching or creates anoverlapping touch with contact point 414. Switch 446 is closed so thatvoltage 454 is conveyed through amplifier 448 to contact point 414.Switches 444 and 468 are open so that amplifiers 422 and 460 have DCvoltages and touch sensor 412 and contact point 415 have zerotime-varying signal. As a result, a touch to touch sensor 412 or contactpoint 415 while not touching contact point 414, results in no measurablesignal and no touch to touch sensor 412 is detected. Signal modifier 452modifies the phase or frequency of voltage 454 so that voltage 454 isdistinguishable from voltages 427 and 464. Preferably, in the case of aphase sensitive touch system, the phase of current measuring devices 428and 462 are set 180° from the phase of current measuring device 450.

If the user of touch system 400 simultaneously touches contact points415 and 414 and touch sensor 412, a portion of current 456 may flow fromthe user's body, through touch capacitance 430 to touch sensor 412, toamplifiers 422 and back to local ground 432, or current 456 may flowthrough touch capacitance 464 of contact point 415, through amplifier460 and back to local ground 432. As current 456 flows through either ofamplifiers 422 or 460, it will be measured by current measuring device428 or 462, and measurements will be conveyed to processor 416. Thus, asa touch on touch sensor 412 or contact point 415 may be detected andmeasured only if the user is simultaneously touching contact point 414.It is noted that a return path for the current provided by touchingcontact point 414 and touch sensor 412 or contact point 415 willgenerally increase the current being measured and thus increase thesignal-to-noise ratio of the current measurements and the resultingsignal collected by the processor. This is especially true whereimpedance 440 is high.

In a third mode of touch system 400 (mode 3) that is similar to mode 2,contact point 415 is activated or made available for activation byclosing switch 468. A touch on contact point 414 or on touch sensor 412can be detected and measured only if the user is simultaneously touchingcontact point 415. A touch to contact point 415 can also be detectedindependent of touching contact point 414 or touch sensor 412. In mode3, switches 444 and 446 are open so that amplifiers 222 and 448, andthus touch sensor 412 and contact point 414, have DC signals. As aresult, a touch to only touch sensor 412 or contact point 414 while nottouching contact point 415 results in no measurable signal and no touchis detected. When switch 468 is closed, voltage 464 is conveyed throughamplifier 460 to contact point 415, and current 470 is measured bycurrent measuring device 462.

In one embodiment of touch system 400, two users can use the touchsystem simultaneously if processor 416 is programmed to switch or togglerapidly between modes 2 and 3. If a first user touches contact point 414continuously and a second user touches contact point 415 continuously,the touch coordinates of each user touching touch sensor 412 can bemeasured because the signals generated by each user on touch sensor 412are distinguishable from each other. According to this embodiment,processor 416 first configures switches 444, 446 and 468 to mode 2,activating contact point 414 with a signal equal to voltage 454. Thepresence of the first user is detected by current change through contactpoint 414, resulting from capacitive contact 458 with the first user.When the first user touches touch sensor 412, a connection with voltage454 via amplifier 448 to contact point 414 causes current 456 to flowthrough the first user's body and into touch sensor 412. The position ofthe first user is measured from the distribution of current throughelectrodes 420, current measuring devices 428 and amplifiers 422. If thesecond user is touching touch sensor 412 during this time, thecapacitive coupling of the second user's body will have a negligibleeffect on currents 456 flowing from the first user into touch sensor412, because the current from the first user's body generates negligiblevoltage on the surface of touch sensor 412. After measuring the firstuser's position, processor 416 changes or toggles from mode 2 to mode 3,thus deactivating contact point 414 and activating contact point 415with voltage signal 464. The presence of the second user is detected bya current change through contact point 415 that results from capacitivecontact with the second user. When the second user touches touch sensor412, a connection with voltage 464 via amplifier 460 to contact point415, causes current 470 to flow through the second user's body and intotouch sensor 412. The touch by the second user to touch sensor 412 ismeasured from the distribution of current in touch sensor 412. Measuringboth the first and second user's position by switching or toggling frommode 2 to mode 3 and from mode 3 to mode 2 can be repeated at a rapidrate of, for example, 5 milliseconds per mode. This will result in theperception of simultaneous detection, even in situations where touchdown and lift off are rapid by human standards. While this embodimentshows a useful two-user device with two contact points 414 and 415, itis readily expandable to more than two users by the addition of morecontact points and their associated circuitry.

In addition to the sequenced multi-user system as described above,current flowing from one contact point to another contact point can beused as an indication of a unique condition. If, for example, two usersare touching their respect contact points in a given application, suchas a two person competitive video game, and a first user touches asecond user, current will flow from one contact point through the firstuser's body, the second user's body, and into the contact point of thesecond user. At any given point in the above example, one contact pointhas voltage applied to it so that it can provide a current when the userassociated with that pad touches the touch screen, while the othercontact point is inactive with no voltage and should have no currentflow. If current for a given pad is detected in the inactive pad, it isan indication that the two users are touching one another. This can beused in a game or other application as an “interference” or “foul”indicator.

Another example of an application of the present invention is withautomobile navigation systems. Automobile navigation systems may havetouch screens that use the principles of modes 2 and 3. Automotivemanufacturers have begun using video displays with touch screens onnavigation systems where the system interface may be too complex forbuttons and dials alone. Navigation system may also be too complex touse while actively driving the vehicle. One solution is to disable thedriver's touches from registering on the navigation system while the caris in motion, but allow a passenger to use the navigation system at anytime. It may also be desirable to allow any passenger to use thenavigation system, or only the passenger sitting in one of the frontseats. Disabling a touch of one or more passengers from registering onthe navigation system may be accomplished by implanting contact pointsor similar sensors in one or more of the vehicle seats. When a usercreates a touch signal in the contact point by sitting in or beingproximate to a seat, the touch system will react according to thesystem's program settings to allow or disallow touches from that user toregister on the navigation system.

In a fourth mode of touch system 400 (mode 4), that is similar to modes2 and 3, both contact points 414 and 415 are activated, preferably byclosing switches 446 and 468. A touch on touch sensor 412 can bedetected and measured only if the user is simultaneously touching or hasactivated contact point 414 or 415 and touch sensor 412. A touch tocontact point 414 or 415 can also be detected independently of touchingtouch sensor 412. In mode 4, switch 444 is open so that amplifiers 422and touch sensor 412 have DC voltage signal at their outputs and nosignal is generated by a touch to touch sensor 412. Switches 446 and 468are closed so that contact point 414 and 415 are driven with a timevarying signal by amplifiers 448 and 460. A touch to contact point 414will couple voltage 454 on contact point 414 to the user's bodyimpedance 434 through touch capacitance 458, causing current 456 to flowthrough current measuring device 450, contact point 414, couplingcapacitance 458, the user's body impedance 434, body-to-ground impedance436, system impedance 440, local ground 432, and amplifiers 422 as thecurrent flows back to touch sensor 412. Processor 416 measures thechange in current 456 and determines if the change in current is above adefined threshold or meets specified signal requirements. If definedrequirements are met, a touch to contact point 414 is registered and maybe communicated from processor 416 to CPU 442.

Mode 4 has an important difference from other modes of touch system 400in that current measurement circuits 428 may each use a phase sensitiveor frequency sensitive demodulator that measures two separate phases orfrequencies, for example, phases that are 90° apart. Also, signalmodifiers 452 and 466 may be set to generate voltages 454 and 464 atseparate phases or frequencies, for example, phases that are 90° apartso that the phase sensitive demodulator 428 may detect currentsresulting from a user touching contact point 414 or 415 and touch sensor412. With these phase or frequency settings, current measuring devices428 are able to yield simultaneous detection of touches to contactpoints 414 or 415 and a position measurement of a touch to touch sensor412.

In fifth mode of touch system 400 (mode 5), touch sensor 412 and contactpoints 414 and 415 are all driven with time varying voltage signals,preferably by closing switches 444, 446 and 468. A touch to touch sensor412 alone may be detected and measured, as will a touch to only contactpoints 414 or 415. Signal modifiers 452 and 466 may adjust the phase orfrequency of voltages 454 and 464 to be distinguishable over each otherand voltage 427, for example, by 180° out of phase with voltage 427 and90° out of phase with each other.

A benefit of mode 5 is improved signal-to-noise ratio for touch signalsgenerated on touch sensor 412, if the user simultaneously touchescontact points 414 or 415. Signal-to-noise ratios are affected in atleast two ways: first, touching a contact point 414 or 415 whiletouching touch sensor 412 provides a local ground path for touch current(as illustrated in the schematic circuit of FIG. 8); and second, inaddition to touch current flowing from touch capacitance 430, through auser's body impedance 434, into earth ground 438, system impedance 440,body-to-ground impedance 436, and local ground 432, current may alsoflow from touch capacitance 430, through a user's body impedance 434,contact point touch capacitance 458 or 464, amplifier 448 or 460, andinto local ground 432.

Another embodiment is where the contact point is adjacent to, and stillseparate from, the sensor. One example is a touch system 500 thatincludes a touch sensor 512 and conductive contact points 414 and 415constructed onto a single substrate 590 that is coated on its topsurface with conductive material, as illustrated in FIG. 9. Alinearization pattern 592 of conductive material, such as silver frit orconductive ink, is printed around the border of touch sensor 512. Wires524 and electrodes 520 may connect to pattern 592 at the four corners oftouch sensor 512. Drive amplifiers, such as amplifiers 422 illustratedin FIG. 7, may be used to power conductive surface 513 of touch sensor512. Contact points 514 and 515 may connect to drive amplifiers, such asamplifiers 448 and 460 in FIG. 7, through wires 580 and 581 that areconnected to conductive electrodes 594 and 596. Contact points 514 and515 and touch sensor 512 are electrically isolated from each other byisolation lines 598 and 599. Isolation lines 598 and 599 may be formedby selectively etching away the conductive material on the surface ofsubstrate 590 or by other methods such as laser ablation.

In another embodiment of a capacitive touch system, such as touch system400, a second touch sensor may replace one or both of contact points 414and 415. In this embodiment, the system may be operated in the same orsimilar modes as system 300. However, a second or more additional touchsensors would each require multiple amplifiers and electrodes such asamplifiers 422 and electrodes 420 with associated current measuringdevices 428 in order to measure and determine a touch to each of thoseadditional touch sensors. An additional touch sensor in a touch systemmay be used for many purposes, for example, to replace a “mouse” used tooperate the system where the location of a touch on the additional touchsensor conveys a right or left mouse button activation or a slidingtouch on the additional touch sensor may perform the same or similarfunction of a mouse scroll. Such a touch system may be configured sothat the primary touch sensor, the additional touch sensor, or both orneither touch sensors are functional only when these touch sensors areactivated or when an additional contact point is also simultaneouslyactivated.

Contact points may have conductive surfaces or may comprise conductiveor resistive materials that are insulated from direct touch by adielectric material, as is common practice with capacitive touchsensors. To “touch” a contact point, it is only necessary thatcapacitive contact be made between a user or an object and theconductive material of the contact point, either by physical touching orby proximity touching. It would be possible, for example in a capacitivetouch system, to implement contact points into a table by installingconductive foil pads under a surface laminate such as Formica. If theuser rests an arm on or close to the table over the foil pad, therewould typically be sufficient signal coupled capacitively to the userfor detection of the user and for injection of measurable current into atouch sensor or contact point. Alternatively, contact points may be madewith a foil sheet or conductive mesh screen that may be placed into orunder the fabric of a seat such as an automobile seat (as describedabove with regard to automobile navigation systems). In anotherexemplary application, contact points may be made with a foil sheet orconductive plate embedded in the housing of a hand-held personal digitalassistant (PDA). A hand-held device such as a PDA is not grounded exceptfor a battery ground, creating a capacitive touch circuit with highimpedance. Therefore, powering the touch surface of the PDA through aseparate touch pad (the embedded conductive material) may reduce thesystem impedance, particularly if the contact point is separatelypowered. An advantage of this embodiment of the invention is that when atouch sensor is powered by simultaneously touching of a contact point oran additional touch sensor, the additional current source provided bythe simultaneous touching improves the sensitivity of the system, evenif there is only one user involved.

In addition to sensing the presence of a user, a touch on a touch sensormay be selectively enabled. Also, in applications such as the automobileseat or the table where contact points are insulated from the user by adielectric material, it is advantageous to drive a contact point withthe highest feasible voltage so that the touch current is maximized.Contact points may be driven with high voltage while touch sensordrivers use low voltage, or vice versa.

Typical magnitudes of electrical parameters for the touch systemsdescribed above, using features of touch system 400 as examples, are:for voltage 427, about 1 to 30 V peak-to-peak at 10 kHz to 200 kHz; forvoltage 454, about 1 to 30 V peak-to-peak at 10 kHz to 200 kHz; forvoltage 464, 1 to 30 V peak to peak at 10 kHz to 200 kHz; for touchcapacitance 430, about 100 to 2000 pf; and for body-to-ground impedance436, about 50 to 2000 pf with a resistance typically less than about 100Ω if a user makes direct electrical contact with ground 438. Bodyimpedance 434 is typically in the range of about 20 to 300 kΩ. Touchsensor 412 has a surface resistance of about 300 to 3000 Ω/□ (ohms persquare) having a surface resistance between any two corners of the touchsensor of about 50 to 500 Ω. Output impedance of amplifiers 422, 448 and460 may be about 0.5 to 100 Ω. System impedance 440 may be about 1 to10,000 pf for an isolated touch system. System impedance 440 may haveresistance less than 0.001 Ω if the touch system is electricallyconnected to ground.

Many embodiments of the present invention have several practical useswithin the field of computer-related games. For example, touch pads maybe integrated into a game user's seat, arm rest, joystick, mouse, or thelike or be activated by pressing a button or series of buttons that aremounted separately or integrated into the game console or otherfurniture associated with the game. A computer game may utilize ananalog touch digitizer and at least one touch pad where activation ofthe pad indicates that the user is ready to play or wants to take a timeout. A computer game with “foul” detection, as described above, mayinclude indicating when players are touching each other or performingactions that violate game rules, such as users taking turns at touchingthe touch sensor in a particular order.

As applied to games, the invention may require that the user or usersplay a game with only one hand because a second hand must maintaincontact with a contact point. This feature would help reduce the numberof hands that are touching a touch sensor during the course of a game,thus reducing obstructions to view of the touch sensor such as when atouch sensor is integrated into a viewable screen. The invention mayalso be used to measure the amount of time a user is touching the touchsensor in comparison to the amount of time the touch sensor is availablefor touching due to activation of a contact point. This feature could bea performance indicator or a method of determining the payment amount ina pay-for-use computer game. The invention may also allow for thecomputer game to display the amount of time the user is “in play” orotherwise available to register a touch to the touch sensor because ofsimultaneously touching a contact point. For example, a border orbackground of a computer game screen may change from red to green when auser is “in play” and may be able to indicate when each of severalplayers is “in play.”

As further applied to games, one embodiment of the invention may beconfigured to allow for playing a team game, for example, each playermay have a contact point but only one player is activated at a time toregister a touch to the touch sensor. Activation of a different playermay be done after an activate player completes a portion of the game,possibly on a fixed time basis or at random times without prior notice.In an alternative team game, each team may include only one contactpoint and the contact point must be momentarily untouched as players onthe same team alternate being “in play.” The game may be configured sothat all the members of a team may be touching the same or differentcontact points before any player is “in play.”

Throughout the above detailed description of the present invention,emphasis has been placed on utilizing various voltage phases and phasechanges to fulfill the objectives of the invention. For example, signalmodifiers 452 and 466 may adjust the phase relationship of voltages 454and 464 relative to voltage 427 and current measuring devices 428, 450and 462 may make phase sensitive current measuring devices. Analternative to using different voltage phases as a way to distinguishbetween voltage signals is to use voltage signal frequencies (asmentioned throughout). If frequencies were used for this purpose,frequency adjusters would replace phase shifters and current measuringdevices would make frequency sensitive current measurements rather thanphase sensitive current measurements.

Where frequency is used to distinguish between signals, it is possiblethat passing multiple frequencies across a touch sensor may result in abuildup of current in some form on the touch sensor. Such a currentbuildup can be reduced by filtering off excess current from the touchsensor with a filter, as may be common in the art.

Although the specific features of the invention are shown in somedrawings and not in others, this is for convenience only as features maybe combined with any or all of the other features in accordance with theinvention. The words “including,” “comprising,” “having,” and “with” asused herein are to be interpreted broadly and comprehensively and arenot limited to any physical interconnection. Moreover, any embodimentsdisclosed in the subject application are not to be taken as the onlypossible embodiments.

Other embodiments will occur to those skilled in the art and are withinthe following claims.

1. A vehicle touch screen system comprising: a touch sensor accessiblefrom a driver position and a passenger position; a first contact pointassociated with the driver position, the first contact point driven witha first signal, the first signal being transferred to the touch sensorthrough a driver in the driver position by a driver touch input on thetouch sensor; a second contact point associated with the passengerposition, the second contact point driven with a second signal, thesecond signal being transferred to the touch sensor through a passengerin the passenger position by a passenger a touch input on the touchsensor; and a processor configured to discern driver touch inputs frompassenger touch inputs based on detection of the first or second signalson the touch sensor, and further configured to determine touch inputlocation on the touch sensor using the detected first or second signals.2. The vehicle touch screen system of claim 1, wherein the touch sensoris disposed over a display.
 3. The vehicle touch screen system of claim1, wherein the touch sensor is a capacitive touch sensor.
 4. The vehicletouch screen system of claim 1, wherein the touch sensor is a resistivetouch sensor.
 5. The vehicle touch screen system of claim 1, wherein thefirst and second contact points are activated by user proximity.
 6. Thevehicle touch screen system of claim 1, wherein the first and secondcontact points are embedded in vehicle seats.
 7. The vehicle touchscreen system of claim 1, wherein the system is configured to disabletouch inputs from users in the driver position when the vehicle is inmotion.
 8. The vehicle touch screen system of claim 1, wherein thesystem is a navigation system.
 9. The vehicle touch screen system ofclaim 1, wherein the processor is further configured to determine touchlocation for simultaneously applied driver touch inputs and passengertouch inputs.
 10. The vehicle touch screen system of claim 1, furthercomprising a touch sensor switch electrically connected to the touchsensor, a first contact point switch electrically connected to the firstcontact point, a second contact point switch electrically connected tothe second contact point, and a power source, and wherein the touchsensor switch and the first and second contact point switches arefurther electrically connected to the power source.
 11. The vehicletouch screen system of claim 10, wherein the touch sensor switch or oneof the first and second contact point switches must be closed for thesystem to determine a location of a touch to the touch sensor.
 12. Thevehicle touch screen system of claim 1, wherein the first and secondcontact points are driven with guard signals to reduce noise in thesystem.
 13. The vehicle touch screen system of claim 1, wherein a drivertouch input completes a first circuit that includes the first contactpoint and the touch sensor and bypasses ground, and a passenger touchinput completes a second circuit that includes the second contact pointand the touch sensor and bypasses ground.
 14. The vehicle touch screensystem of claim 13, wherein the touch sensor is a capacitive touchsensor and a sensitivity of the touch sensor is enhanced by bypassingground in completing the first and second circuits.